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Strom R.G.,CAS National Astronomical Observatories | Strom R.G.,Netherlands Institute for Radio Astronomy | Strom R.G.,University of Amsterdam | Strom R.G.,James Cook University | And 6 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2013

The giant radio galaxy 4C 73.08 has been observed with the Westerbork Telescope at a wavelength of 21 cm. The radio map obtained is a significant improvement upon previous maps in terms of the combination of high dynamic range, sensitivity and angular resolution. The new map shows that the jet, previously thought to be one-sided, is probably symmetrical with one arm almost lost in the background of extended lobe emission. The brighter, more compact lobe also displays more intense emission from its hotspot and jet. The jets line up well with the nucleus and hotspots, although the hotspot on one side deviates from the lobe major axis. The unusual feature of the radio source's morphology is the existence of curved ridges running transverse to the source major axis. Three of the other galaxies in the 4C 73.08 group are also weak radio sources. We further detect radio emission from the foreground galaxies NGC 2957 and 2963, which form a small group. A background galaxy has double radio components of moderate size which we have mapped; there is an optical companion at the same redshift. Another extended source may be associated with a Two Micron All Sky Survey galaxy. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. Source


Chen R.,CAS National Astronomical Observatories | Peng B.,CAS National Astronomical Observatories | Peng B.,Joint Laboratory for Radio Astronomy Technology | Strom R.G.,Netherlands Institute for Radio Astronomy | And 5 more authors.
Astronomy and Astrophysics | Year: 2011

Context. There is a group of about twenty galaxies around the giant radio galaxy (GRG) DA 240 which we are studying to investigate the environment of the radio source. We have noted that 11 members are aligned with the radio emission (Peng et al. 2004, A&A, 415, 487). The alignment occurs within a small angle similar to the width of the GRG radio lobes, and there may be some physical causal relationship. After finishing observations of the four candidates not included in Paper I, we have completed our study of the brighter members of the sample of galaxies around DA 240. Aims. We aim to see if more galaxies have similar redshifts to the host galaxy of DA 240, to confirm the galaxy grouping and further study their distribution. Methods. Spectra of the four candidate galaxies were obtained with the 2.16 m spectroscopic telescope at XingLong observing station of the NAOC, and the galaxies' positions were established with respect to the radio emission. We have discovered two more members associated with the group of galaxies around DA 240. In addition, the work of other researchers provides one other new member. Results. The number of confirmed galaxies associated with the DA 240 group has increased by almost a quarter to 20. There are now 14 galaxies (including the host) lying along the major axis of the radio source. We further consider the relationship of the group to adjacent galaxy associations, noting that it may form a binary pair with the slightly closer UGC 3957 group. They both lie on the periphery of the much more substantial cluster, Abell 576. © 2011 ESO. Source


Chen R.,CAS National Astronomical Observatories | Chen R.,Chinese Academy of Sciences | Peng B.,CAS National Astronomical Observatories | Peng B.,Chinese Academy of Sciences | And 6 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2012

The optical field of the giant radio galaxy (GRG) 4C 73.08 has been spectroscopically investigated to look for companions to the host 7Zw 292. We have taken spectra of 12 candidates and have determined redshifts for all of them. When combined with the previously known redshift of 7Zw 292, we find that the radio source is accompanied by a small group of nine galaxies, of which the GRG host is the brightest. Seven members of the group lie within 350kpc of 7Zw 292, gathered around the brighter, more compact component of the double radio source. The whole group has a velocity dispersion of ∼270kms -1. We discuss this result in the light of the X-ray emission which has been detected from the region. 4C 73.08 follows the pattern found in other GRGs of being associated with a small group, but not falling in a rich cluster. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS. Source


Chen R.,CAS National Astronomical Observatories | Chen R.,Chinese Academy of Sciences | Peng B.,CAS National Astronomical Observatories | Peng B.,Chinese Academy of Sciences | And 6 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2012

We have investigated the environment of the giant radio galaxy NGC 315 with its associated group of galaxies selected by their spectroscopic redshifts. Observations were made with the 2.16-m optical telescope at Xinglong Station of the National Astronomical Observatories of China. In addition to 25 galaxies near NGC 315 with published redshifts, we have successfully determined 21 new redshifts of candidates, five of which are previously unknown members of the NGC 315 galaxy group. We examine and discuss the spatial structure and kinematics of this group (which is part of the Perseus-Pisces filament). Nearly 40 per cent of its members are concentrated near NGC 315, close to the emission from its brighter radio jet. The X-ray luminosity implied by the optical velocity dispersion is higher than that derived empirically from observations of other groups, suggesting that X-ray-emitting gas within the NGC 315 group has a low density. This may be one reason for the size of the radio source. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS. Source


Chen R.,CAS National Astronomical Observatories | Peng B.,CAS National Astronomical Observatories | Peng B.,Joint Laboratory for Radio Astronomy Technology | Strom R.G.,CAS National Astronomical Observatories | And 4 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2011

We have investigated galaxies around NGC 6251 to search for an associated group. Our main goal is to study the environment around the giant radio galaxy to better understand the reasons for its size and structure. To this end, we have made spectroscopic observations with the 2.16-m optical telescope at Xinglong Station of the National Astronomical Observatories of China (NAOC) and obtained spectra of 45 objects (including four likely stars). The redshifts give us 10 new galaxies in a group, which are in addition to seven previously known members. The 17 galaxies' positions are compared with the radio emission. The optical velocity dispersion of group members within 0.7Mpc of NGC 6251 is not consistent with that expected from correlation curves of X-ray luminosity L x versus velocity dispersion σ r. We briefly discuss this result, suggesting that in the NGC 6251 group, the density of X-ray emitting gas is unusually low, and this is the main reason for the size of the radio source. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS. Source

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